A little outdated but still relevant:
This year, about a billion T-shirts have been made for the United States market, or four for every back. Domestic mills produced about 609 million outerwear-style T- shirts and produced another 300 million meant to be worn as underwear. About 108 million shirts have been imported.

T-shirts are the only clothing sold not just in stores, but also on the street, in gasoline stations, bowling alleys, movie theaters and zoos. A single shirt can fetch as little as $5 or as much as $150 when sold in boutiques. Even better, in Manhattan’s Times Square, three shirts can sell for as low as $10.

Large makers like Fruit of the Loom Inc. and the Hanes division of Sara Lee Corporation, together account for more than 50 percent of the domestic outerwear T-shirt market, with Fruit of the Loom having a somewhat higher share than Hanes. But retailers buy only about 15 percent of their shirts directly from the manufacturers. The rest filter through wholesalers who either print T-shirts themselves or sell to independent, entrepreneurial style printers.

Yes classic indeed.